I read this thread rather quickly, so forgive if this suggestion was included among the other excellent and detailed advice.
I work through a 501 (c) 3 and am the sole full time employee. So I get to wear all the hats. I have found - and sometimes too late! - that some software manufacturers will sell at a good discount to bona fide not-for-profits. Just one example is Quark. I paid a hefty amount to buy a single use copy only to discover later that I could have saved a good percentage of the cost.

Typically, you will need to transmit the IRS letter of recognition of your organization as tax exempt. I have scanned that to my hard drive so that I can print it out to fax it or attach it to an email.

I have picked up some good tips here ... thanks!